When descending into airports, aircraft must decrease altitude and airspeed. If the landing must be aborted, engine thrust must be increased to safely stop descent and restore climb as needed to attempt another landing. Thrust recovery includes the process of increasing thrust from a given operating state of the engine.
To ensure responsiveness to demand for increased thrust, pilots operate their engines during the final approach at a higher spin rate or thrust setting than optimal for descent. This practice produces noise and pollution over the entire portion of the approach. For a flight that aborts an attempted approach (less than 5% of all flights), the decision to do so is likely to occur close to the airport, after having wasted jet-fuel up to that decision time before needing more thrust from the engines.
Accordingly, there is a need to produce reliable, adequate thrust within the response time required by pilots while minimizing the wasted fuel burned and noise produced during approach.